Projector

ABSTRACT

A projector having a cross-dichroic prism ( 260 ) synthesizing three kinds of red, green, and blue light emitted from liquid crystal panels ( 250, 252, 254 ); and a projection lens ( 270 ) projecting the synthesized light and also having polarizing plates ( 251, 253, 255 ) disposed on the optical paths between the corresponding liquid crystal panels ( 250, 252, 254 ) and the cross-dichroic prism ( 260 ) includes a lens element ( 256 ), serving as an optical element for compensating chromatic aberration of magnification, which is formed on and integrally with one surface of the polarizing plate ( 251 ) disposed on the light path of the red light and which adjusts the size of the projected image screen of the red light extending along at least a predetermined direction so as to be nearly equal to those of the projected image screens of the other kinds of color light extending along the predetermined direction.

TECHNICAL FIELD

The present invention relates to a projector, and more particularly, itrelates to compensation of chromatic aberration of magnification-of aprojected image screen.

BACKGROUND ART

A projector projecting and displaying a color image includes anillumination optical system, a color-light-separating optical system,liquid-crystal panels for corresponding kinds of separated color light,a color-light--synthesizing optical system, and a projection opticalsystem. Light emitted from the illumination optical system is separatedinto three kinds of red, green, and blue light by thecolor-light-separating optical system, and the three kinds of colorlight are modulated by corresponding liquid crystal panels so as togenerate corresponding images. Then, these images are synthesized by thecolor-light-synthesizing optical system and are projected by theprojection optical system. The projection optical system focuses thethree kinds of synthesized color light on a projection screen so as toproject a color image onto the projection screen. Unfortunately, theprojection optical system generally has chromatic aberration ofmagnification, thereby often causing a problem in that the sizes ofprojected image screens of the three kinds of color light are differentfrom one another. In order to solve the above problem, a lens forcompensating chromatic aberration of magnification can be included in alens set forming the projection optical system; however this structuremakes the projection optical system larger. As a countermeasure againstthis problem, a technique for compensating the above-mentioned chromaticaberration of magnification by providing a lens element or a prismelement in a space from the emitting surface of each electroopticaldevice to the incident surface of the color-light-synthesizing opticalsystem, more particularly, by providing a lens element or a prismelement on the incident surface of a color-light-synthesizing prismwithout making the projection optical system larger has been known (forexample, see Patent Document 1). Also, the color-light-synthesizingprism serving as the color-light-synthesizing optical system issometimes formed so as to have a convex or concave dichroic surface (forexample, see Patent Document 2).

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2000-206450 (Claim 1, FIG. 1)

Patent Document 2: Japanese Unexamined Patent Application PublicationNo. 11-38210

Unfortunately, since the space from the emitting surface of eachelectrooptical device to the incident surface of thecolor-light-synthesizing prism is narrow, disposition of an additionallens element or prism element in the space makes the space narrower,thereby deteriorating the cooling feature of the electrooptical device.Also, it is often difficult to fabricate a lens element or a prismelement in order to dispose it on the incident surface of thecolor-light-synthesizing prism, when the shape and the function of thecolor-light-synthesizing prism are taken into consideration.

DISCLOSURE OF INVENTION

The present invention has been made in view of the above problems.Accordingly, it is an object of the present invention to provide aprojector having a new structure, taking both cooling feature andworkability of each electrooptical device into reconsideration on theoccasion of compensating chromatic aberration of magnification of aprojection optical system by disposing an optical element forcompensating chromatic aberration of magnification in the space from theemitting surface of the electrooptical device to the incident surface ofa color-light-synthesizing optical system.

A projector according to the present invention includes an illuminationoptical system emitting illumination light; a color-light-separatingoptical system separating the illumination light into three kinds ofred, green, and blue light; electrooptical devices receiving the threekinds of color light separated by the color-light-separating opticalsystem, converting them into corresponding kinds of light for formingimages of the corresponding kinds of color light in accordance withimage signals of the corresponding kinds of color light, and emittingthem; a color-light-synthesizing optical system synthesizing the threekinds of color light emitted from the electrooptical devices; aprojection optical system projecting the light synthesized by thecolor-light-synthesizing optical system; and polarizing plates disposedon the light paths of the corresponding kinds of color light between thecorresponding electrooptical devices and the color-light-synthesizingoptical system and further includes an optical element which adjusts thesize of a projected image screen of at least one of the three kinds ofcolor light extending along at least a predetermined direction so as tobe nearly equal to those of the other kinds of color light extendingalong the predetermined direction and which is formed on and integrallywith one surface of the corresponding polarizing plate so as to serve asan optical element for compensating chromatic aberration ofmagnification.

With this structure, since the polarizing plate and the correspondingoptical element for compensating chromatic aberration of magnificationare integrated into one substrate, the space for these components can beeffectively utilized, thereby minimizing deterioration of the coolingfeature of the electrooptical device. Also, the structure has anadvantage in that it is easier to integrate the optical element forcompensating chromatic aberration of magnification, such as a lenselement or a prism element, with the corresponding polarizing plate thanto integrate the optical elements for compensating chromatic aberrationof magnification with a color-light-synthesizing prism.

Also, in the above case, the projector may have a structure in which theparent material of the polarizing plate disposed on the light path ofthe red light is composed of glass or a light-transmissive resin, theparent material of the polarizing plates disposed on the light paths ofthe green and blue light are composed of sapphire or quart crystal, andthe optical element for compensating chromatic aberration ofmagnification is disposed only on the light path of the red light. Sincethe polarizing plate disposed on the light path of the red light has awider temperature allowance than those disposed on the light paths ofthe other kinds of color light, in place of thermally conductive quartzcrystal or sapphire, glass or resin having better workability than thequartz crystal or sapphire can be used as the parent material of thepolarizing plate used for the red light. Accordingly, a lens element ora prism element can be easily formed on an integrally with thepolarizing plate used for the red light by making use of its parentmaterial.

A projector according to the present invention includes an illuminationoptical system emitting illumination light; a color-light-separatingoptical system separating the illumination light into three kinds ofred, green, and blue light; electrooptical devices receiving the threekinds of color light separated by the color-light-separating opticalsystem, converting them into corresponding kinds of light for formingimages of the corresponding kinds of color light in accordance withimage signals of the corresponding kinds of color light, and emittingthem; a color-light-synthesizing optical system synthesizing the threekinds of color light emitted from the electrooptical devices; aprojection optical system projecting the light synthesized by thecolor-light-synthesizing optical system; and angle-of-view compensatingfilms disposed on the light paths of the corresponding kinds of colorlight between the corresponding electrooptical devices and thecolor-light-synthesizing optical system and further includes an opticalelement which adjusts the size of a projected image screen of at leastone of the three kinds of color light, extending along at least apredetermined direction, so as to be nearly equal to those of the otherkinds of color light extending along the predetermined direction andwhich is formed on and integrally with one surface of the correspondingangle-of-view compensating film so as to serve as an optical element forcompensating chromatic aberration of magnification.

With this structure, since the angle-of-field compensating film and thecorresponding optical element for compensating chromatic aberration ofmagnification are integrated into one substrate, the space for thesecomponents can be effectively utilized, thereby minimizing deteriorationof the cooling feature of electrooptical device. Also, it is easier tointegrate the optical element for compensating chromatic aberration ofmagnification, such as a lens element or a prism element, with thecorresponding angle-of-field compensating film than to integrate theoptical elements with a color-light-synthesizing prism.

In addition, each of the above-described projectors is characterized inthat, when the optical axis of the projection optical system is shifted(moved) in parallel to at least one of two directions mutuallyperpendicular to the system optical axis, the optical axis of theoptical element for compensating chromatic aberration of magnificationis shifted in parallel to a predetermined direction, following the shiftof the optical axis of the projection optical system. With thisstructure, even when the projection optical system is shifted,compensation of chromatic aberration of magnification of a projectedimage screen can be properly performed. The system optical axis statedhere is a hypothetical axis formed by a series of optical elementsdisposed on the light path upstream of the projection optical system andsubstantially coincides with the center axis of light fluxes incident onthe projection optical system.

Meanwhile, in the above-mentioned case, the optical element preferablyhas no refraction feature on a plane extending orthogonal to thepredetermined direction and including the generating line thereof andhas a refraction feature on a plane extending orthogonal to thegenerating line thereof. With this structure, of differences in sizes ofthe projected image screens of the corresponding kinds of color light,caused by the chromatic aberration of magnification of the projectionoptical system, differences in sizes of the projected image screensextending along a direction perpendicular to the generating line can bereduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the structure of an overall optical system of aprojector according to an embodiment of the present invention.

FIG. 2 is a plan view illustrating a partial structure of the opticalsystem shown in FIG. 1, in the vicinity of a cross-dichroic prism of thesame.

FIG. 3 illustrates states of projected image screens of the projectorincluding the optical system shown in FIG. 2.

FIG. 4 is a plan view illustrating another partial structure of theoptical system shown in FIG. 1, in the vicinity of the cross-dichroicprism of the same.

FIG. 5 illustrates states of projected image screens of the projectorincluding the optical system shown in FIG. 4.

FIG. 6 is a plan view illustrating another partial structure of theoptical system shown in FIG. 1, in the vicinity of a cross-dichroicprism of the same.

FIG. 7 illustrates states of projected image screens of the projectorincluding the optical system shown in FIG. 6.

FIG. 8A illustrates the structure formed by a polarizing plate and anoptical element for compensating chromatic aberration of magnificationwhen a convex lens for compensating chromatic aberration ofmagnification shown in FIG. 2 is replaced with a prism.

FIG. 8B illustrates the structure formed by a polarizing plate and anoptical element for compensating chromatic aberration of magnificationwhen a concave lens for compensating chromatic aberration ofmagnification shown in FIG. 4 is replaced with a prism.

FIG. 9 is a plan view illustrating another partial structure of theoptical system shown in FIG. 1, in the vicinity of the cross-dichroicprism of the same.

FIG. 10 is a plan view of the optical system, illustrating directions ofparallel shifts of the optical axes of optical elements for compensatingchromatic aberration of magnification in accordance with a shift of theprojection lens in the X-axis direction.

FIG. 11 is a perspective view of the optical system, illustratingdirections of parallel shifts of the optical axes of the opticalelements for compensating chromatic aberration of magnification inaccordance with a shift of the projection lens in the Y-axis direction.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a plan view of the schematic structure of an overall opticalsystem of a projector according to an embodiment of the presentinvention. The projector includes an illumination optical system 100;dichroic mirrors 210 and 212; reflecting mirrors 220, 222 and 224; anincident-side lens 230; a relay lens 232; three field lenses 240, 242and 244; three liquid crystal panels 250, 252 and 254 serving aselectrooptical devices; polarizing plates 251, 253 and 255 correspondingto the foregoing liquid crystal panels; a cross-dichroic prism(color-light-synthesizing prism) 260 serving as acolor-light-synthesizing optical system; and a projection lens 270serving as a projection optical system.

The illumination optical system 100 includes a light source 110 emittinglight fluxes in a predetermined direction; a first lens array 120; asecond lens array 130; a polarization-conversing element 140; areflecting mirror 150; and a superimposing lens 160. The first andsecond lens arrays 120 and 130 form an integrator optical system forsubstantially uniformly illuminating the three liquid crystal panels250, 252 and 254 occupying the illumination region thereof.

The light source 110 has a light source lamp 112 serving as a radiallight source emitting radial rays; and a concave mirror 114 emitting theradial light emitted from the light source lamp 112 so as to besubstantially parallel light fluxes. As the light source lamp 112, ahigh-pressure discharge lamp such as a metal halide lamp or ahigh-pressure mercury lamp is generally used. Although a paraboloidmirror is preferably used as the concave mirror 114, an ellipsoidalmirror or a spherical mirror may be used in place of the paraboloidmirror.

The first lens array 120 is formed by a plurality of first small lenses122. The second lens array 130 is formed by a plurality of second smalllenses 132 corresponding to the plurality of respective first smalllenses 122. Substantially parallel light fluxes emitted from the lightsource 110 are divided into a plurality of partial light fluxes by thefirst and second lens arrays 120 and 130 and are incident on thepolarization-conversing element 140. The polarization-conversing element140 has a function of converting non-polarized light into predeterminedlinearly polarized light, for example, s-polarized light or p-polarizedlight and emitting it. Accordingly, the plurality of partial lightfluxes incident on the polarization-conversing element 140 is convertedinto respectively predetermined linearly polarized light and is emitted.The plurality of partial light fluxes emitted from thepolarization-conversing element 140 is reflected at the reflectingmirror 150 and is incident on the superimposing lens 160. Most of theplurality of partial light fluxes incident on the superimposing lens 160is superimposed on the liquid crystal panels 250, 252 and 254 occupyingthe illumination region by a superimposing action of the superimposinglens 160. As a result, each of the liquid crystal panels 250, 252 and254 is almost uniformly illuminated.

The two dichroic mirrors 210 and 212 form a color-light-separatingoptical system 214 separating light emitted from the illuminationoptical system 100 into three kinds of red (R), green (G) and blue (B)light. The first dichroic mirror 210 allows a red light component oflight emitted from the illumination optical system 100 to be transmittedtherethrough and reflects blue and green light components thereat.

The red light transmitted through the first dichroic mirror 210 isreflected at the reflecting mirror 220, passes through the field lens240, and reaches the liquid crystal panel 250 for the red light. Thefield lens 240 has a function of collecting each of the partial lightfluxes transmitted therethrough so as to be parallel to the main opticalaxis (center axis) thereof. The field lenses 242 and 244 disposed infront of the corresponding liquid crystal panels act likewise.

Of the blue and green light reflected at the first dichroic mirror 210,the green light is reflected at the second dichroic mirror 212, passesthrough the field lens 242, and reaches the liquid crystal panel 252 forthe green light, while the blue light is transmitted through the seconddichroic mirror 212 and then through a relay lens system including theincident-side lens 230, the relay lens 232, and the reflecting mirrors222 and 224. The blue light transmitted through the relay lens system isfurther transmitted through the field lens 244 and reaches the liquidcrystal panel 254 for the blue light.

Meanwhile, the relay lens system is used for the blue light in order toprevent reduction in utilization efficiency of the blue light which iscaused by the fact that the light path of the blue light is longer thanthose of the other kinds of color light, in other words, in order totransmit the blue light incident on the incident-side lens 230 to theemitting-side lens (field lens) 244 without change.

Each of the three liquid crystal panels 250, 252 and 254 serving aselectrooptical devices has a function as a light-converting device whichconverts the corresponding color light incident thereon into light forforming an image in accordance with a given image signal and emits theconverted light. Each of the liquid crystal panels 250, 252 and 254generally has polarizing plates disposed on the incident and emittingsurface sides of light so as to adjust the polarizing direction of thecorresponding color light. Meanwhile, the polarizing plates disposed onthe emitting surface sides of the liquid crystal panels 250, 252 and 254are shown in FIG. 1 by reference numbers 251, 253 and 255, respectively.

The cross-dichroic prism 260 functions as a color-light-synthesizingoptical system synthesizing the three kinds of color light emitted fromthe three liquid crystal panels 250, 252 and 254. The cross-dichroicprism 260 has a dielectric multilayer film reflecting red light thereatand another dielectric multilayer film reflecting blue light thereat,wherein the two films are formed along the interfaces of fourrectangular prisms in an approximate X-shape. The three kinds of colorlight are synthesized by these dielectric multilayer films so as to formsynthetic light for projecting a color image. The synthetic lightgenerated by the cross-dichroic prism 260 is emitted toward theprojection lens 270. The projection lens 270 projects the syntheticlight onto a projection screen 300 so as to display a color image on thesame.

Meanwhile, as shown in FIG. 1, the direction of the system optical axisAx is defined as the Z axis (the traveling direction of light is apositive Z direction), a direction parallel to a line of intersectionbetween the dielectric multilayer film-reflecting the red light thereatand the dielectric multilayer film reflecting the blue light thereat isdefined as the Y axis (a direction upward the plane of the figure is apositive Y direction), and a direction perpendicular to the Z and Y axesis defined as the X axis (a leftward direction when facing toward thepositive z direction is a positive X direction).

In the meantime, since the projection lens 270 generally has chromaticaberration of magnification, the magnification of a projected imagescreen varies in accordance with the color, that is the wavelength, oflight incident on the projection lens 270. Accordingly, as shown in FIG.3(a), the sizes of image screens IR, IG, and IB formed from thecorresponding kinds of R, G, and B color light and projected onto ascreen by a projector having no function of compensating its chromaticaberration of magnification are sometimes different from one another.Meanwhile, FIG. 3(a) illustrates a case where the image screens becomelarger in the order from light having a longer wavelength to lighthaving a shorter wave length, that is, a case satisfying the condition:the image screen IR of the red light<the image screen IG of the greenlight<the image screen IB of the blue light.

As a countermeasure against the above problem, the projector accordingto the present invention has an optical element for compensatingchromatic aberration of magnification incorporated on the light path ofthe red light. In this structure, the optical element for compensatingchromatic aberration of magnification is a convex lens 256 forcompensating chromatic aberration of magnification, formed on andintegrally with the emitting surface of the polarizing plate 251disposed on the light path of the red light. For better understanding ofthe convex lens 256 for compensating chromatic aberration ofmagnification, FIG. 2 illustrates a partial structure of the opticalsystem shown in FIG. 1, in the vicinity of the cross-dichroic prism 260.The convex lens 256 for compensating chromatic aberration ofmagnification has a function of magnifying the size of the image screenof the red light projected onto a screen and locating the projectedimage screen of the red light between the projected image screens of thegreen and blue light. As a result, in the above-mentioned projector, asshown in FIG. 3(b), differences in sizes of the projected image screensIR, IG, and IB of the corresponding colors, caused by the chromaticaberration of magnification of the projection lens 270 become smaller,and these sizes become nearly equal to one another.

Also, as shown in FIG. 5(a), there is sometimes a case where the sizesof the image screens IR, IG, and IB formed from the corresponding kindsof R, G, and B color light and projected onto a screen by a projectorhaving no function of compensating the chromatic aberration ofmagnification are become larger in the order from light having a shorterwavelength to light having a longer wavelength, that is, a casesatisfying the condition: the image screen IR of the red light>the imagescreen IG of the green light>the image screen IB of the blue light.

As a countermeasure against such a case, the case can be dealt with byemploying an optical system as shown in FIG. 4. In this optical system,a concave lens 257 for compensating chromatic aberration ofmagnification is formed on and integrally with the emitting surface ofthe polarizing plate 251 disposed on the light path of the red light.The concave lens 257 for compensating chromatic aberration ofmagnification has a function of reducing the size of the projected imagescreen of the red light and locating the projected image screen of thered light between the projected image screens of the green and bluelight. As a result, in the above-mentioned projector, as shown in FIG.5(b), differences in sizes of the projected image screens IR, IG, and IBof the corresponding colors, caused by the chromatic aberration ofmagnification of the projection lens 270 become smaller, and these sizesbecome nearly equal to one another.

In the meantime, since each polarizing plate interposed between thecorresponding liquid crystal panel and the cross-dichroic prism absorbslight and generates heat when the light is transmitted therethrough, asubstrate having the polarizing plate fixed thereto is preferablycomposed of thermally conductive sapphire or quartz crystal. However,since the red light causes the polarizing plate to generate a lessamount of heat than the green or blue light, the parent material or thebase material of the polarizing plate 251 disposed on the light path ofthe red light may be composed of glass such as borosilicate glass orquartz glass or a light-transmissive resin. Since a glass substrate or aresin substrate can be more easily processed so as to have a curvedsurface than a sapphire substrate or the like, a lens element can beeasily formed on and integrally with the emitting surface of thepolarizing plate 251 composed of one of these parent materials by, forexample, polishing the emitting surface.

Meanwhile, in the case of the structure shown in FIG. 2 or 4, the sizeof the image screen IR of the red light is not always needed to fall ina size range between the sizes of the image screens IG and IB of theother kinds of color light. For example, the size of the image screen IRof the red light may be arranged so as to be nearly equal to that of theimage screen IG of the green light or the image screen IB of theblue-green light. Even with this arrangement, a variance in the sizes ofthe image screens of the three kinds of color light can be decreased asa whole. As is seen from the above description, the phrase “the sizes ofthe image screens are nearly equal to one another” in the presentinvention and this Description means not only that the sizes of thethree image screens are equal to one another but also that differencesin sizes of the image screens become smaller in comparison to the casewhere no countermeasure for compensating the chromatic aberration ofmagnification is employed at all.

FIG. 6 is a plan view illustrating another partial structure of theoptical system shown in FIG. 1, in the vicinity of the cross-dichroicprism 260. In this structure, the emitting-surface side of thepolarizing plate 251 disposed on the light path of the red light has acylindrical convex surface (serves as a cylindrical convex lens element)256A having a generating line parallel to the Y axis. Also, in thiscase, as shown in FIG. 7, the sizes of the image screens IR, IG, and IBof the corresponding kinds of color light in the lateral direction ofthe image screens can be arranged so as to be nearly equal to oneanother (a change from (a) to (b) shown in FIG. 7). That is, ofdifferences in sizes of the projected image screens of the correspondingkinds of color light, caused by the chromatic aberration ofmagnification of the projection lens 270, differences in sizes of theprojected image screens extending along a direction perpendicular to thegenerating line (the X axis direction) can be reduced. Meanwhile, FIGS.6 and 7 illustrate an example of adjusting the sizes of the imagescreens in the case of satisfying the condition: the image screen IR ofthe red light<the image screen IG of the green light<the image screen IBof the blue light. However, when the sizes of the image screens satisfythe condition: the image screen IR of the red light>the image screen IGof the green light>the image screen IB of the blue light, the sizes ofthe image screens IR, IG, and IB of the corresponding kinds of colorlight in the lateral direction of the image screens can be made nearlyequal to one another, by forming the emitting-surface side of thepolarizing plate 251 disposed on the light path of the red light so asto have a cylindrical concave surface (so as to serve as a cylindricalconcave lens element) having a generating line parallel to the Y axis.

Also, when only the sizes of the image screens in the Y axis directionare adjusted, it is required only that a polarizing plate provided withan emitting surface having a lens element which serves as an opticalelement for compensating chromatic aberration of magnification and whichhas a cylindrical curved surface whose generating line is set so as tobe parallel to the X axis direction be used.

Although FIG. 6 illustrates an example case where the emitting surfaceis a circularly cylindrical curved surface, the emitting surface is notlimited to such a shape, and it may be an elliptically cylindricalcurved surface. That is, it is required only to have a curved surfacehaving no refraction feature on a plane including the generating linethereof and having a refraction feature on a plane orthogonal to thegenerating line thereof. In the description stated here, the phrase“having no refraction feature on a plane including the generating lineof the curved surface” means that, when the light path of light passingthrough the curved surface is projected onto a plane including thegenerating line of the curved surface, the projected light path isviewed as not being refracted. Also, the phrase “having a refractionfeature on a plane including the generating line of the curved surface”means that, when the light path of light passing through the curvedsurface is projected onto a plane orthogonal to the generating line ofthe curved surface, the projected light path is viewed as beingrefracted.

In addition, although the convex or concave surface of the emittingsurface of the polarizing plate 251 is formed so as to have a curvedlens shape in the previous description, since the lens shape often has alarge radius of curvature and is very thin, the emitting surface mayhave a prism shape by approximating the curved surface with flat planes.FIGS. 8A and 8B illustrate the above-mentioned structure, wherein FIG. 8a illustrates the lens shape formed so as to provide a prism-shapedconvex surface (prismatic convex surface) 256B having a ridge lineextending parallel to the Y axis to approximate the emitting surface ofthe polarizing plate 251 with flat planes, and FIG. 8B illustrates thelens shape formed so as to provide a prism-shaped concave surface(prismatic concave surface) 257B having a ridge line extending parallelto the Y axis to approximate the emitting surface of the polarizingplate 251 with flat planes. Even with one of these structure, the sizesof the image screens IR, IG, and IB of the corresponding kinds of colorlight in the X axis direction of the image screens can be arranged so asto be nearly equal to one another. That is, of differences in sizes ofthe projected image screens of the corresponding kinds of color light,caused by the chromatic aberration of magnification of the projectionlens 270, differences in sizes of the projected image screens extendingalong a direction perpendicular to the generating line (the X axisdirection) can be reduced.

In the meantime, a lens element or a prism element is formed on (oradded to) the polarizing plate 251 disposed on the light path of the redlight among the three kinds of red, green and blue-green color light inthe foregoing description. However, if the processing similar to thatapplied on the polarizing plate 251 is also applicable on the polarizingplates 253 and 255 disposed on the light paths of the green light andthe blue-green light, respectively, in place of or together with thepolarizing plate 251, a lens element or a prism element may be formed on(or added to) the polarizing plate 253 and/or 255 so as to reducedifferences in sizes of the projected image screens formed from thethree kinds of red, green, and blue-green color light as a whole.Meanwhile, the shape of the lens element or the prism element can bedecided according to the already described contents, depending on howthe sizes of the projected image screens are compensated.

Also, although some of projectors have a structure in whichangle-of-view compensating films are interposed between thecorresponding liquid crystal panels 250, 252 and 254 and thecross-dichroic prism 260 so as to improve contrast of the correspondingprojected image screens, in such a case, a lens element or a prismelement similar to that added to the above mentioned polarizing platemay be formed on the emitting side of each of the angle-of-viewcompensating films, in place of the above-mentioned polarizing plate. Inthe case of the angle-of-view compensating film, since absorption oflight is not needed to be taken into consideration so much, glass or alight-transmissive resin can be used as the parent material of the filmregardless of a kind of color light. Accordingly, by using glass or alight-transmissive resin, the angle-of-view compensating film disposedon the light path of any kind of color light, of which the size of theprojected image screen is needed to be adjusted, can be processed. FIG.9 illustrates an example of such a structure in which angle-of-viewcompensating films 281, 283 and 285 are interposed between thecorresponding liquid crystal panels 250, 252 and 254 and thecross-dichroic prism 260, the angle-of-view compensating film 281disposed on the light path of the red light has the convex lens 256formed on the emitting surface thereof, and the angle-of-viewcompensating film 285 disposed on the light path of blue light has theconcave lens 257 formed on the emitting surface thereof. When the sizesof the image screens lie, for example, in the following order: the imagescreen IR of the red light<the image screen IG of the green light<theimage screen IG of the blue light, the above-mentioned structure can beused so as to perform expanding compensation for making the size of theimage screen IR of the red light closer to the image screen IG of thegreen light and to perform contracting compensation for making the sizeof the image screen IB of the blue light closer to the image screen IGof the green light, whereby the sizes of the image screens of thecorresponding kinds of color light can be nearly equal to one another asa whole.

In addition, some of projectors have a structure in which its projectionlens 270 can be shifted (moved) in parallel to two directions (the Xaxis direction and the Y axis direction) mutually perpendicular to thesystem optical axis Ax. In such a case, it is preferable that each ofthe optical elements 256, 256A, 256B, 257 and 257B for compensatingchromatic aberration of magnification integrally formed with thepreviously described polarizing plate or angle-of-view compensating filmbe shifted (moved) in parallel to a predetermined direction, followingthe shift of the projection lens 270, so that chromatic aberration ofmagnification of the projected image screen be properly compensated.

FIG. 10 is a plan view of the optical system, illustrating directions ofparallel shifts of the optical axes of the optical elements forcompensating chromatic aberration of magnification in accordance with aparallel shift of the optical axis of the projection lens 270 in the Xaxis direction, and FIG. 11 is a perspective view of the optical system,illustrating directions of parallel shifts of the optical axes of theoptical elements for compensating chromatic aberration of magnificationin accordance with a parallel shift of the optical axis of theprojection lens 270 in the Y axis direction. Meanwhile, in the followingdescription, the combined optical elements of the previously describedpolarizing plates and corresponding optical elements for compensatingchromatic aberration of magnification are respectively represented byreference numbers 290R, 290G, and 290B.

When the optical axis of the projection lens 270 is shifted in thedirection of the X axis with respect to the system optical axis AX, adirection of a parallel shift of the optical axis of the combinedoptical element 290G compensating color light passing the two kinds ofdielectric multilayer films is the same as that of the parallel shift ofthe optical axis of the projection lens 270. Also, a direction of theparallel shift of the optical axis of each of the combined opticalelements 290R and 290B compensating color light reflected at either oneof the two kinds of dielectric multilayer films is opposite to that ofthe parallel shift of the optical axis of the projection lens 270. FIG.10 illustrates the above-mentioned situations. In the figure, theparallel shift of the optical axis of the projection lens 270 in apositive or negative direction of the X axis is respectively shown bythe solid-line arrow X1 or the broken-line arrow X2, and a direction ofthe parallel shift of the optical axis of each of the combined opticalelements 290R, 290G and 290B corresponding to the above parallel shiftis shown by the same solid-line arrow X1 or broken-line arrow X2.

When the optical axis of the projection lens 270 is shifted in parallelto the direction of the Y axis with respect to the system optical axis,the optical axis of any of the combined optical elements 290R, 290G and290B is shifted in parallel in the same direction as the movingdirection of the optical axis of the projection lens 270. FIG. 11illustrates the above-mentioned situation. In the figure, the parallelshift of the optical axis of the projection lens 270 in a positive ornegative direction of the Y axis is respectively shown by the solid-linearrow Y1 or the broken-line arrow Y2, and a direction of the parallelshift of the optical axis of each of the combined optical elements 290R,290G and 290B corresponding to the above parallel shift is shown by thesame solid-line arrow Yl or broken-line arrow Y2.

Meanwhile, it is preferable that a shift amount of the optical axis ofeach of the combined optical elements 290R, 290G and 290B in these casesbe the same as that of the optical axis of the projection lens 270.However, sometimes the combined optical elements 290R, 290G and 290Bcannot be shifted to such an extent that the projection lens 270 isshifted, depending on a space where these optical elements are disposed.In such a case, these optical elements are preferably shifted by lessthan but as close as possible to the shift amount of the optical axis ofthe projection lens 270.

Although the present invention has been described above in detail, thepresent invention is not limited to the above-described embodiments andcan be embodied in a variety of modes without departing from the spiritof the present invention. For example, the following modification ispossible.

In order to form a lens element or a prism element on and integrallywith one surface of the polarizing plate or the angle-of-viewcompensating film, the lens or the prism may be bonded on the incidentsurface or the emitting surface thereof, or a thin resin film which iscured by irradiation with light such as ultraviolet ray or by heat maybe attached on the incident surface thereof. Also, the convex surface ofthe convex lens for compensating chromatic aberration of magnificationand the concave surface of the concave lens for compensating chromaticaberration of magnification are not limited to being spherical and maybe aspheric.

In addition, although the electrooptical device of the projector is atransmissive liquid crystal panel in the above-described embodiments,the electrooptical device is not limited to the above-mentioned panel.For example, a micro-mirror device performing optical modulation bycontrolling reflecting light in accordance with an angle of amicro-mirror may be used. In other words, a variety of devices whichmodulate light in accordance with an image signal so as to form an imageare applicable to the electrooptical device.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a projection TV and a projectorused for screening a film, presentation, or the like.

REFERENCE NUMERALS

100: illumination optical system

214: color-light-separating optical system

240, 242, 244: field lenses

250, 252, 254: liquid crystal panels

251, 253, 255: polarizing plates

256: lens for compensating chromatic aberration of magnification

257: concave lens for compensating chromatic aberration of magnification

256A: cylindrical convex surface for compensating chromatic aberrationof magnification

256B: prism-shaped convex surface for compensating chromatic aberrationof magnification

257B: prism-shaped concave surface for compensating chromatic aberrationof magnification

260: cross-dichroic prism

270: projection lens

281, 283, 285: angle-of-view compensating films

290R, 290G, 290B: combined optical elements

300: projection screen

AX: system optical axis

1. A projector comprising: an illumination optical system emittingillumination light; a color-light-separating optical system separatingthe illumination light into three kinds of red, green, and blue light;electrooptical devices receiving the three kinds of color lightseparated by the color-light-separating optical system, converting theminto corresponding kinds of light for forming images of thecorresponding kinds of color light in accordance with image signals ofthe corresponding kinds of color light, and emitting them; acolor-light-synthesizing optical system synthesizing the three kinds ofcolor light emitted from the electrooptical devices; a projectionoptical system projecting the light synthesized by thecolor-light-synthesizing optical system; and polarizing plates disposedon the light paths of the corresponding kinds of color light between thecorresponding electrooptical devices and the color-light-synthesizingoptical system, and the projector further comprising an optical elementwhich adjusts the size of a projected image screen of at least one ofthe three kinds of color light extending along at least a predetermineddirection so as to be nearly equal to those of the other kinds of colorlight extending along the predetermined direction and which is formed onand integrally with one surface of the corresponding polarizing plate soas to serve as an optical element for compensating chromatic aberrationof magnification.
 2. The projector according to claim 1, wherein theparent material of the polarizing plate disposed on the light path ofthe red light is composed of glass or a light-transmissive resin, theparent materials of the polarizing plates disposed on the light paths ofthe green and blue light are composed of sapphire or quart crystal, andthe optical element for compensating chromatic aberration ofmagnification is disposed only on the light path of the red light.
 3. Aprojector comprising: an illumination optical system emittingillumination light; a color-light-separating optical system separatingthe illumination light into three kinds of red, green, and blue light;electrooptical devices receiving the three kinds of color lightseparated by the color-light-separating optical system, converting theminto corresponding kinds of light for forming images of thecorresponding kinds of color light in accordance with image signals ofthe corresponding kinds of color light, and emitting them; acolor-light-synthesizing optical system synthesizing the three kinds ofcolor light emitted from the electrooptical devices; a projectionoptical system projecting the light synthesized by thecolor-light-synthesizing optical system; and angle-of-view compensatingfilms disposed on the light paths of the corresponding kinds of colorlight between the corresponding electrooptical devices and thecolor-light-synthesizing optical system, and the projector furthercomprising an optical element which adjusts the size of a projectedimage screen of at least one of the three kinds of color light,extending along at least a predetermined direction, so as to be nearlyequal to those of the other kinds of color light extending along thepredetermined direction and which is formed on and integrally with onesurface of the corresponding angle-of-view compensating film so as toserve as an optical element for compensating chromatic aberration ofmagnification.
 4. The projector according to claim 1, wherein theoptical element is a lens element or a prism element.
 5. The projectoraccording to claim 1, wherein, when the optical axis of the projectionoptical system is shifted in parallel to at least one of two directionsmutually perpendicular to the system optical axis, the optical axis ofthe optical element for compensating chromatic aberration ofmagnification is shifted in parallel to the foregoing direction,following the shift of the optical axis of the projection opticalsystem.
 6. The projector according to claim 5, wherein an amount of theparallel shift of the optical axis of the optical element forcompensating chromatic aberration of magnification is the same as thatof the parallel shift of the optical axis of the projection opticalsystem.
 7. The projector according to claim 5, wherein an amount of theparallel shift of the optical axis of the optical element forcompensating chromatic aberration of magnification is smaller than thatof the parallel shift of the optical axis of the projection opticalsystem.
 8. The projector according to claim 5, wherein thecolor-light-synthesizing optical system is a cross-dichroic prism havingtwo kinds of dielectric multilayer films formed along the interfaces offour rectangular prisms in an approximate X-shape.
 9. The projectoraccording to claim 8, wherein, when the optical axis of the projectionoptical system is shifted in parallel to an axial direction parallel tothe line of intersection between the two kinds of dielectric multilayerfilms, a direction of the parallel shift of the optical axis of theoptical element for compensating chromatic aberration of magnificationis the same as that of the parallel shift of the optical axis of theprojection optical system.
 10. The projector according to claim 8,wherein, when the optical axis of the projection optical system isshifted in parallel to an axial direction perpendicular to the line ofintersection between the two kinds of dielectric multilayer films and tothe system optical axis, a direction of the parallel shift of theoptical axis of the optical element for compensating chromaticaberration of magnification, compensating color light passing throughthe two kinds of dielectric multilayer films, is the same as that of theparallel shift of the optical axis of the projection optical system, anda direction of the parallel shift of the optical axis of the opticalelement for compensating chromatic aberration of magnification,compensating color light reflected at any one of the two kinds ofdielectric multilayer films, is opposite to that of the parallel shiftof the optical axis of the projection optical system.
 11. The projectoraccording to claim 1, wherein the optical element has no refractionfeature on a plane extending orthogonal to the predetermined directionand including the generating line thereof and has a refraction featureon a plane extending orthogonal to the generating line thereof.